86 SEVENTH REPORT. 



tion has been added and mixed with the culture fluid the conditions 

 are less nniforin than in the control vials. It would seem more likely 

 that the sugar solution through a specific physiological influence causes 

 the individuals either to divide less evenly than usual, or to grow less 

 uniformly after division. That cane srigar has in other cases a specific 

 influence on growth processes has been demonstrated by studies in ex- 

 perimental embryology: 



The bearing of these results on current theories as to the origin of 

 variation will be discussed in the complete paper. ' 



The points brought out in this preliminary communication may be 

 summarized as follows, it being understood that they are not stated as 

 final conclusions, but are subject to such modifications as may be neces- 

 sary when our data are completely reduced: 



1. Paramecia in our experiments when reared in relatively small 

 volumes of culture fiuid — 10 c. c. or less — show a progressively lower 

 mean length the longer they remain under such conditions. 



2. Tn the case of pure strains — i. e., gron])s of individuals coming 

 from a single ancestor — reared under the conditions mentioned in 1, 

 the variation, in length of body for the fraternity so reared is reduced 

 from 8 to 10 per cent below that of the general population, in the 

 samples analyzed up to this time. 



3. By the addition of cane sugar solution to the culture fluid so 

 that as a maximum there were 3 parts of m/\ cane sugar to each 100 

 parts culture fluid, in the series of experiments here reported, the varia- 

 tion in length of body in the series of selected ancestry was increased 

 until it equalled the variation in the same character shown by a random 

 sample of unknown ancestry from a "wild" culture. 



I wish here to acknowledge my indebtedness to the Carnegie Insti- 

 tution of Washington for a grant in aid of biometric work of which 

 this forms a part. 



I^niversity of Micliigan. 



FURTHER EXPERIMENTS ON STATIC FUNCTION.* 



L. MURBACH. 



At the 1003 meeting of The Michigan Academy of Science, a short 

 report was given of some experiments made to determine to what ex- 

 tent the jellyfish, Gonionemus, depends on its otocyst organs for regu- 

 lating its position in space. This jellyfish was chosen as it is very 

 easily obtainable for several months during the summer at the Marine 

 Biological Laboratory, and especially because it has more definite 

 or characteristic movements in vertical directions than any other 

 medusa known to the writer. The experiments were not considered 

 conclusive, especialy as they indicated a result that I had not expected. 

 The subsequent discussion determined me to make further experiments. 



* Work done at the Marine Biological'Laboratory, Wood's Hole, Mass., — Season 1904. For facil- 

 ities I am indebted to the Laboratorj-. 



